Rotary pump



R. STEVENSON ROTARY YPUMP Filed July 4, 1,942

Jan. 9,'1945- s sheevsfsneet 1 INVENTOR @agg/ fe rfa/1.9012

, Bmw

ATTORNEYS Jan. 9, 1945.

R. STEYENSON ROTARY PUMP Filed July 4, 1942 5 Sheets-Sheet 2 Jari. 9, 1945. R. sTEvENsoN ROTARY PUMP Filed Ju1y.4, 1942 5 sheets-Sheet s Hz'nv PRESSDRE Ubs. sq.|-]

mwa@ wmammm Il .ruabzob 5000 R.P.M.

50o R PM HEAD PRESSURE [iba Sq.,|-]

H aan @PR SSURE [1bs.sq. In]

M .Rov s Ww m LA w B,

Robe/ ma; mmzmmwtn Fu-.200

- Patented `lan. 9,1945

Robert Stevenson, Providence, B. 1.,' assignor to Stevenson Engineering Corporation, a corporation of Rhode Island Application July 4, 1 942, Serial No. 449,740

4 claims. (C1. 10s-44o) Y This invention relates to a rotary puirnp of the type'in which the rotor is rotatably mounted relative to a cylindrical casing and there are vane members in the rotor which are moved into and out of the rotor for engagement with the casing during the rotation of the rotor in the casing;

' In the use of rotary pumps of this character Asome diiliculty has been encountered in controlling the vane members because of the pressure which has been developed in the pump. If springs or other mechanical action is depended upon for operating the members, faults are liable tooccur.

One of the objects of this invention is to provide avarie in the rotor which will be controlled entirely by the forces developed in the pump during operation and thus an elimination' of the use of springs, vgears or other mechanically-acting parts.

Another object; oi this invention is to provide a. construction whereby the shaping of the vane the forces tending to move the varies may be selected to obtain the'desired function.

. Another object of the invention is to provide an arrangement whereby the amount oi pressure that may be developed willV be limited only by the strength of materials used. v A l Another object o the invention is to provide a. pump which at a certain predetermined revolutions per minute will maintain a constant head or pressure on the discharge side of the pump by reason of the vanes .of the rotorautomatically opening to such extent as is necessary to allow slip of some of the fluid being pumped Apast the vanes. Y

Another object of the invention is to provide a pump in which no reliefvalve -or bypass is needed by reason of the action of the rotor vanes serving to accomplish the function that the reliei valve or bypass ordinarily accomplishes.

With these and other vobjects in view, the invention consistsv ofxcertain novel features of cou-V .20 to provide surface areas may be so arranged that struction, 'as will be more yfully described and particularly pointed out in the appended. claims.

In the accompanying drawings: Fig. 1 isa central sectional view through the Fig. 2 isa sectional view taken at substantially right anglesto Fig. 1 and on line 2-2 of Fig. 1.

Fig; 3 is a'fragmental sectional view on anl enlarged sca1e,1sh`owing one of the vane members, a parto!` the rotor, andl a part of the casing.

Fig. 4 is an end view of the rotoralone. Fig. 5 is a perspective vieW of the vane member alone.

Figs. 6 and 7 dare fragmental sectional views with diagrammatic illustration of certain forces which act on the vane.

' Figs. 8, 9 and 10 arenfragmental sectional views of modified forms of vane members.

. ,Fi'gs. 11, 12 and 13 are graphs showing difieren I relationships which may be had.

, In proceeding with this invention I provide a casing and a rotary member within the casing with a series of vanes-in the rotor which Willmove relative to. the rotor and will force iiuid from the intake port "to' the outlet port of the casing. There are several forces which I deal with in connection with the design of the vanes of the rotor. One of these forces that must be taken into consideration in the particular construction of the vanes which I provide, is the centrifugal force which is exerted on the vane by the rotation of the rotor in the casing. Thusthe center of gravity of my vane member with reference -to the point or center about which it may 4tum or rotate is one force with which I deal.

' Another force with which I deal is that of the resistance of the iiuid being pumped to movement by the vane which might be-call'ed the inertia of the fluid being pumped and this force will exert a certain moment upon the vane tending to rotate it in a direction opposite to that 'direction resulting from the action of the centrifugal force. The area with which I calculate the center of eiort of this force will be important upon the action '.-of the vane. This force will also vary with the weight ofthe iluid being pumped. Another force with which I deal is that of the pressure'developed in the casing during the 'series action of the vanes and is that pressure' in that compartment of lthe casing to which the vane is exposed or subjected to the pressure o this 'uid, and the particular shape of the vane which maycause an exposure of areas in-one position or another position. and the amount of these 'areas will affect the action of the vane.

From the forces at work in the operation of my pump as above indicated, it will be readily apparby the particular design or shaping of the vane and will not appreciably be a function ofthe revolutions per minute or speed of rotation of the rotor. Thus with the above guide in mind I may design a vane which at a certain number of revo- .lutions per minute will pump a fluid of a known y specific gravity or weight up to a certain -head or pressure and atthis point the`van'e will open and will cease to pump or build up pressure any further, the control of the vane being wholly by these pressures which are developed within the pump itself.

With reference to the drawings, the casing consists of a body part III of generally ringshape having a lining 9 with a cylindrical inner surface II while there are end sections l`2 and I3 abutting the opposite ends of this 'bodymember I0 and held snugly thereagainst by suitable means such as screw bolts. Dowels I4 'extend throughl bosses |55 and I5 to align the parts of the casing.

' Ihe end sections I2 and I3 are provided with ball bearings I1, and section I2 is provided with a construction I3 similar to that shown in my copending application,v Serial No. 388,015. These bearings are held in position by the cover members I9 and 29 secured' by bolts 2| to the respeta--4 tive end sections I2and I3. The bearings I1 and.

I1 are` in lan axial alignment with each other in eachof the end sections I2 and I3 for the recep tin of a shaft designated generally 25 in-these i bearings. The bearings are mounted eccentricab ly with reference to the cylindrical surface. Il so that a positive movement of the vanes of the pump may be had.

The shaft 25 is enlarged as at 25, and has secured thereto a rotor member 21 so .that this rotor member will be rotated by driving of the` shaft. The rotor 21 is cylindrical in shape and is provided with a plurality of arcuate recesses 2l in its cylindrical surfaces, the surfaces each pro-` viding a good bearing support .29 for a vane member designated generally 33 and shown in Perspective in Fig. for freely rockably mounting' the same in the recess 28. As shown in Fig. 2 the cylindricalouter surface-3l of the rotor will come closest to the. inner cylindrical surface II of the casing lining 9 at the upper portion of Fig, 2, where vthe spacing of the rotor and the casing will be rather close, while at the lower portion of Fig. 2 the spacing'of the surface of the rotor and the inner surface of the casing lining will be at the maximum distance.

The vane member 30'has a cylindrical surface 32 which is mutilated by being cut parallel to the axis of the cylinder 'at a 4point to one side of its mined in order that calculations of the centrifugal -force may be had. Inasinuch as the portion of this vane on either side ofthe slot is-symmetrical vwith reference to a line through the center of the arc of the vane it will be quite readilyapparent that'by reason of the` solid portion of the vane between these twoside portions,.or the part of the vane at the end. of the' slot willcause the center of gravityto be onith'at'side ofthe axial line" through the center. This will be vlocated in .the trailing side of the center of rotation of the vane with respect to the direction of rotation of the rotor.'l By usual'- and known mathematics in engineering. practice'the center of gravity may be determined, yand I have illustrated in Fig.' 6 at' 50 such location, and I'have drawn a line 5I from the center of the axis of rotation of the shaft 26 through this'center of gravity, and have also drawn a line 52 representing the perpendicular distance from a radial line 5I -to the .Center 39 of the vane. Therefore it will be apparent that there is a force acting along. the line 5I with a moment proportional to the distance of the line p 52 tending to rotate the vane to .cause its edge 53 to contact the inner cylindrical surface II of the casing. This represents a centrifugal force and will varywith the speedof Vrotation of the rotor and with the positionof the vane in its recess.v It is a force tending to'force contact of the edge 53 with the casing at all times. If the surfaceis moved closer to the radial line 54 through the center in Fig. 6 .therewill be an increase in the mass and also the center of gravity center to presenta side 33 insubstantially a sin- A asfollows.

As the rotor rotates in the direction of the arrow .shown in Fig. 2 on the centershaft 25, centrifugal force. will be developed in each of the varies and if this is to one side of the center 39 of tle vanel (see Fig. 3) there .will be a tendency to turn the vane about'the axis 33 which is the center of the socket or recess 23.A In Fig. 6

will move closer toward the center line/arid the radius 52 will be decreased; Jthe increase of the mass -about counteracts the shortening of the L radius 52, but for any given configuration orshaping of the blade calculation should be made that a determination of 4the exact enect may be hadr The inertia pressure will be that which the fluid exerts in opposition tothe movement of the rotor and may be illustrated by Fig. '1. The surface of the vanes subjected to this pressure will vbe that which extendsfor the entire width of tie rotor.and that portion of the vane which extends into. the space between vthe periphery 3| of the rotor and the inner surface I I of the liner 9. This surface is a rectangle and the center of this recltangle will be that at which the force will be ugal force forces it. This pressure will vary with I have .illustrated a section -through'the center of the vane and it will be readily apparent that the center of gravity of the vane must be deterthe`weight of the iiuid being pumped', the revolutions per minute and the distance of the periphery 3| from the surface II which varies because of the eccentricity. of the rotor mounting.

A third force dealt with is that caused bythe pressure of the biiuid, itself to which the vane is subjected. Referring particularly to Fig'. 3, the area 33 between the rotor and its casing will contain fluid at some'pressure namely the head of the pumped fluid. Ihe uid will engage the surface 33 and also the surface 35 and the pressure of the'fluid willpress upon each portion of the surface in an amount equal to the pressure ofthe fluid in this area. The pressure along some of these surfaces will tend to rotate the vane 30 about .its center 33 (see Fig. 3) in one direction, while posite direction. For illustrative purposes I have broken upthese surfaces into different sections in Figs. 3 and 5 so that the action of the uid pressure may be more clearly appreciated. With reference to Fig. 5 the section ofthe surface 33 between the parallel lines designated zo disstance apart, and between the` parallel lines bounded'by the surface 35 and the edge of the vane, and denoted "a distance in a section which will be effective as represented by the arrows 40.

(Fig. 3) tending to force the vane member away yin Fig. 5. If ahigh speed pump is found necesfrom the surface I I. In this relationship the presl tain 'head pressure and thereafter any increase. in headpressure will cause the vanes to separate' from the surface Il suiiiciently to. bypass all excess uid. Q l

This contact pressure does increase as the rotor is speeded up, due to the increase in centrifugal force in the construction which I lhave illustrated saary a different design in the vane may be had to move the center of gravity nearer tothe center line and thus diminish this contact pressure if less wear or friction'is desirable.

-It will valso be readily apparent that the characteristics of this pump may be readilychanged by merely'removing vanes of one designfsuch as face 35 extending from the topedge 33 down- A.

' wardly to the line extending perpendicular from the center' of rotation of the vane to surface 35 would be effective also to move the member the same direction as the area heretofore mentioned, or would supplement the force tending to move the vane 30 away from the surface I l Area l c which is the same in dimension as the area b being on the opposite side of the center 39 would tend to force the vane 30 toward the surface H while the area d which is the remaining area of the surface would also tend lto force the vane 30 toward the surface I l. Thus we have areas a" plus b. tending to force the vane in A lone direction while the areas c plus d are tendingto force the vane in the opposite direction. The areas b and c being equal provide.

a balanced area and the area d being slightly larger than the area a would provide a greater unbalanced area than the extent of the remainin'g at surface in the slotted area and thus a differential of pressure tending to force the vane 30 against the surface li and thus hold them in engagement. It will of course be apparent that if I move the line or surface 35 nearer or on the other side of the center of rotation 39 there will be a change in the relative areas a,and 12, c and d and a different diierential of these pressures will result. l

In order to. learn the true behavior that may be expected of the-vanes I must add those forces tending to rotate the vane in a counter-clockwise direction as seen in Fig. 3 and subtract from this the forces tending to rotate the .-vane in a clockwise direction as shown in Fig'. 3. A resultant force for the contact pressure at the point 53 between the vane and the inner surface of the .casing may thus be determinedat known weights `of fluids pumped and at a certain number of revolutions per minute of the rotor.

It will be readily apparent that with these variables I may so design the vane and'select the speed that at a'certain speed of the rotor I will obtain a certain head or pressure developed in the pumped fluid and a certain contact pressure between the vane and casing. A graph illustrating the headl pressure plotted against the contact pressure shows in Fig. 11 a selection of values where the contact pressure increases as the -head pressure `increases. In Fig. 12 the selection 'of values such that the contact pressure remains constant even though the head pressure increases, while in Fig. 13 I show a selection of values whereshown in Fig. 5 and dropping in their place vanes of a differentl design. Thus by merely havingsuch parts as the vanes interchangeable the characteristics of the pump may be changed radically and I may utilize a-pump for widely varying work byA merely changing the vanes thereof.

, In Fig. 9 I have shown a design of vane 60 in which the'center of gravity is moved further from the center of rotation and the weight of the vane decreased. In Fig. 10 theopposite is true, as

here the center of gravity of the vane 6 l is moved closer to ,the center of rotation and the weight of the vane increased; also in both of -these designs the pressure of the iiuid in the pocket will act upon the vane similarly to the action heretofore explained but different values, -will be obtained;

In Fig. 8 I have'- shown a somewhat diffrent design with the weight of the vane 62 at one side (the trailing side) of the center of rotation with respect to the motor and the inner surface on arc of a circle.

It will of course be' plain that as the rotor turns in Vthe direction shown by the arrowin Fig. 2 on the center shaft 26 liquid Will be picked up the .through the inlet 43 fed through conduit Tand then by rotation of the vane member asthe eecentricity occurs the Huid will be forced out through the discharge opening lili as the vane member is squeezed toward a position to reduce the volume as at l5 or the -volume of the area 38 as heretofore described. 1 claim: Y 1. In a rotary pump, a casing having a cylindrical compartment therein, a cylindrical rotor eccentrically mounted with reference to the central axis of said compartment and provided with a plurality of recesses in its peripheral cylindrical surface each recess having anarcuate surface of cylindrical generation, a vane member in each recess having a cylindrical arc providing a bearing surface engaging the surface ofsaidfrecess each member rockable into engagement with the inner cylindrical surface of the casing, and each member being moved by reason of ,the rotation of the rotor and by reason of the relatively eccentric mounting of the rotorV and the casing; each member being slotted between its ends from one edge of said flat surface toward-I the opposite edge thereof to present a surface ai; an angle to said flat 'surface whereby said flat surface and said slot formed surface are pressed upon by the iiuid in the compartment contacting the member, the shaping of said slot being such as to so relate the fiat surface and slot formed surface that the desired differential of fluid pressures exerted on said bythe contact pressure will become .nil at a cersent a surface extending at right angles to the' 4 asoman last named surfaces'may exist to urge the mem- -4.` The rotary pump as set forth in claim E. `bei` in the direction desired. vwherein theslot is so shaped land sized as to pre 2. The rotary pump as set, forth in claim 1 sent 'a surface extending at right angles to the wherein the slot is so shaped and sized -as to exsaid hat surface .and oi' aexbent greater in an tend inwardly from onefedge to a point' beyondl 5 unbalanced area than the extent of the remainthe axial center of thevane: ingiiat surface in the slotted area.

3. The rotary pump-as set forth-in claim 1 wherein the slet is se shaped end sized es to pre- RoBER'rsTEvENsoN- said at surface. i0 

